---
title: "Reference: Answer Relevancy | Metrics | Evals | Kastrax Docs"
description: Documentation for the Answer Relevancy Metric in Kastrax, which evaluates how well LLM outputs address the input query.
---

# AnswerRelevancyMetric ✅

The `AnswerRelevancyMetric` class evaluates how well an LLM's output answers or addresses the input query. It uses a judge-based system to determine relevancy and provides detailed scoring and reasoning.

## Basic Usage ✅

```typescript
import { openai } from "@ai-sdk/openai";
import { AnswerRelevancyMetric } from "@kastrax/evals/llm";

// Configure the model for evaluation
const model = openai("gpt-4o-mini");

const metric = new AnswerRelevancyMetric(model, {
  uncertaintyWeight: 0.3,
  scale: 1,
});

const result = await metric.measure(
  "What is the capital of France?",
  "Paris is the capital of France.",
);

console.log(result.score); // Score from 0-1
console.log(result.info.reason); // Explanation of the score
```

## Constructor Parameters ✅

<PropertiesTable
  content={[
    {
      name: "model",
      type: "LanguageModel",
      description: "Configuration for the model used to evaluate relevancy",
      isOptional: false,
    },
    {
      name: "options",
      type: "AnswerRelevancyMetricOptions",
      description: "Configuration options for the metric",
      isOptional: true,
      defaultValue: "{ uncertaintyWeight: 0.3, scale: 1 }",
    },
  ]}
/>

### AnswerRelevancyMetricOptions

<PropertiesTable
  content={[
    {
      name: "uncertaintyWeight",
      type: "number",
      description: "Weight given to 'unsure' verdicts in scoring (0-1)",
      isOptional: true,
      defaultValue: "0.3",
    },
    {
      name: "scale",
      type: "number",
      description: "Maximum score value",
      isOptional: true,
      defaultValue: "1",
    },
  ]}
/>

## measure() Parameters ✅

<PropertiesTable
  content={[
    {
      name: "input",
      type: "string",
      description: "The original query or prompt",
      isOptional: false,
    },
    {
      name: "output",
      type: "string",
      description: "The LLM's response to evaluate",
      isOptional: false,
    },
  ]}
/>

## Returns ✅

<PropertiesTable
  content={[
    {
      name: "score",
      type: "number",
      description: "Relevancy score (0 to scale, default 0-1)",
    },
    {
      name: "info",
      type: "object",
      description: "Object containing the reason for the score",
      properties: [
        {
          type: "string",
          parameters: [
            {
              name: "reason",
              type: "string",
              description: "Explanation of the score",
            },
          ],
        },
      ],
    },
  ]}
/>

## Scoring Details ✅

The metric evaluates relevancy through query-answer alignment, considering completeness, accuracy, and detail level.

### Scoring Process

1. Statement Analysis:
   - Breaks output into meaningful statements while preserving context
   - Evaluates each statement against query requirements

2. Evaluates relevance of each statement:
   - "yes": Full weight for direct matches
   - "unsure": Partial weight (default: 0.3) for approximate matches
   - "no": Zero weight for irrelevant content

Final score: `((direct + uncertainty * partial) / total_statements) * scale`

### Score interpretation
(0 to scale, default 0-1)
- 1.0: Perfect relevance - complete and accurate
- 0.7-0.9: High relevance - minor gaps or imprecisions
- 0.4-0.6: Moderate relevance - significant gaps
- 0.1-0.3: Low relevance - major issues
- 0.0: No relevance - incorrect or off-topic

## Example with Custom Configuration ✅

```typescript
import { openai } from "@ai-sdk/openai";
import { AnswerRelevancyMetric } from "@kastrax/evals/llm";

// Configure the model for evaluation
const model = openai("gpt-4o-mini");

const metric = new AnswerRelevancyMetric(
  model,
  {
    uncertaintyWeight: 0.5, // Higher weight for uncertain verdicts
    scale: 5, // Use 0-5 scale instead of 0-1
  },
);

const result = await metric.measure(
  "What are the benefits of exercise?",
  "Regular exercise improves cardiovascular health, builds strength, and boosts mental wellbeing.",
);

// Example output:
// {
//   score: 4.5,
//   info: {
//     reason: "The score is 4.5 out of 5 because the response directly addresses the query
//           with specific, accurate benefits of exercise. It covers multiple aspects
//           (cardiovascular, muscular, and mental health) in a clear and concise manner.
//           The answer is highly relevant and provides appropriate detail without
//           including unnecessary information."
//   }
// }
```

## Related ✅

- [Prompt Alignment Metric](./prompt-alignment)
- [Context Precision Metric](./context-precision)
- [Faithfulness Metric](./faithfulness)